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J Cell Biol. 2009 November 30; 187(5): 584.
PMCID: PMC2806583
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Aki1 helps centrioles stay tight

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When Aki1 is missing, a cell makes multipolar spindles (green).

Duplicated centrioles are codependent, remaining attached until the end of mitosis. An unlikely protein helps hold the structures together by enlisting one of the tethers that connects sister chromatids, Nakamura et al. show.

Replicated pairs of centrioles relocate to opposite ends of a dividing cell, but the members of each pair remain linked until the end of mitosis. Researchers are starting to unravel how cells control this connection and have already found overlap with the mechanisms that join and part sister chromatids. Centrioles harbor some members of the cohesin complex that lashes chromatids together. The enzyme separase, which cleaves sister chromatids, also splits up centriole pairs.

Nakamura et al. discovered that centrosomes harbor the protein Aki1, which is involved in epidermal growth factor signaling. But when they investigated further, the team found that Aki1 also promotes centriole togetherness. In cells lacking the protein, centriole pairs divorce prematurely, resulting in multipolar spindles. These cells trip the spindle checkpoint and eventually commit suicide.

The cohesin component Scc1 prevents centrioles from splitting too soon, the researchers showed. Aki1 sticks to Scc1 and another cohesin component, SA-2. The results suggest that Aki1 helps direct Scc1 to the centrosome, where it can fasten centrioles together. The next step, the researchers say, is determining why Aki1 helps connect centrioles but not sister chromatids.

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